This invention relates generally to a dynamic variable geometry fitting system for continuously maintaining a secure fit of an external appliance to a body segment, and, more particularly to, a variable geometry system for use with a lower-limb-prostheses.
Lower-limb amputees typically have difficulty maintaining a comfortable, yet secure attachment of their prosthesis to their residual limb (residuum). The volume of the residuum fluctuates both throughout the day and periodically as a result of normal physiological mechanisms. The amputee can detect very small changes in residuum volume. These volume variations often will decrease stability and cause maldistribution of weight-bearing forces, increase locomotion effort, exacerbate insecurity and even cause detachment of a suction-retention socket.
The socket is the mechanical connection between a lower-limb prosthesis and the amputee""s anatomy. As such, the quality of socket fit is usually the most critical determinant of the amputee""s satisfaction with his prosthesis. The precise fitting of the socket and the maintenance of a precise fit are extremely important to the amputee""s comfort, skin integrity, sense of ambulatory security and stability, and locomotion effort.
When an adequate socket fit is finally obtained by the prosthetist, frequently after much trial and error fitting often requiring several check sockets, this fit cannot easily be maintained. Modern fabrication techniques using advanced tools such as CAD/CAM may reduce the iterations required to achieve an initial socket fit. Even using these techniques, initial precise socket fit is frequently lost due to natural volumetric changes of the residuum. Unfortunately, such volumetric change of the residuum is unavoidable. Such change can occur hourly, daily and monthly. For many amputees, the residuum is in a constant state of volumetric flux.
Modern Medial-Lateral (ML) transfemoral (TF) sockets are very sensitive to residuum volume variations which can cause, late in the day, intolerable pain in the groin. This is because the M-L socket is designed to carry about 40% of the load with soft-tissue hydraulic pressure and about 60% by ischial tuberosity support. When the tissue shrinks, the hydraulic support diminishes rapidly. The volume shrinkage then drops the TF residuum into the socket causing its medial brim to load excessively the tissue over the ischial ramus and adductor longus.
A volume change of just 0.2% in a 1500 ml transfemoral total-contact socket can alter the amputee""s perception of ambulatory security. Further, a volume change of 1% was sensed as a xe2x80x9csloppy fitxe2x80x9d by wearers of transfemoral (TF) total-contact, suction-retention sockets. A volume change of 5-6% can cause detachment of a suction-retention socket.
Transtibial (TT) amputees typically have a diurnal variation in residuum volume that requires the addition of one to several single-ply stump socks, from morning to evening, in order to maintain a tight fit. For the typical TT residuum (girth=100 mm; L=150 mm) and stump sock thickness (t=2 mm), two of these sock additions can amount to a volume change of about 2.7%. A residuum volume change of such magnitude, without compensation, is intolerable. For this reason, some TT amputees must continue to don greater numbers of socks during the day in order to maintain a satisfactory fit. Large and frequent volumetric changes of the TT residuum make it difficult to achieve and maintain proper socket contact pressures and compression. Consequently, TT amputees are often unable to utilize effectively and benefit from the suction-retention socket, which requires a tight, non-leaking fit in order to maintain the suction needed to retain the TT prosthesis. This consequence is very unfortunate because a poorly fitting suction socket is usually intolerable, so such afflicted TT amputees may be forced to abandon use of their prostheses. The efficacy of both TF and TT lower-limb prostheses is often reduced due to uncompensated soft-tissue volume variations, which are unavoidable and occur regularly.
Further, suction pressure during the swing phase and positive pressure during the stance phase, of the walking cycle, with a suction socket, has been shown to be beneficial to the TT amputee""s residuum skin and tissue health. Severe lesions, cysts and abrasion have actually been cured by use of a suction socket by TT amputees. This is especially true with a dysfunctional vascular system in the residuum, and such vascular dysfunction is the leading cause of TT amputations.
A further difficulty with all of these present day socket-fitting means is that when the residuum swells, the intra-socket pressure will become intolerable when the residuum swells, and could even result in ischemia (i.e., pinching of the capillaries stops blood flow to tissue), if the socks are not removed in a timely fashion.
Today, prosthetists most often manage residuum volume shrinkage by adding socks, making new sockets or by internal padding of existing sockets. These approaches are entirely inadequate to accommodate natural diurnal volume changes and the weekly and monthly volume variations of the ill, the diabetic, the kidney dialysis patient and the menstruating woman. Furthermore, the accommodation of residuum atrophy of new amputees, accomplished by manufacturing multiple sockets, is very expensive, even using modern CAD/CAM fabrication.
Many different types of variable-volume sockets have been proposed and tried, but none of these apparatuses address adequately the fundamental problem of automatically adjusting for volumetric change of the residuum.
It is the object of this invention to provide a dynamic variable geometry fitting system for use in, for example, lower-limb prostheses that continuously maintains a secure fit of an external appliance to a body segment.
It is a further object of this invention to provide a variable geometry system for use in lower limb prostheses, which automatically accommodates to the amputee""s normal variation in residuum volume while maintaining a secure fit.
It is still a further object of this invention to provide a low-compliance attachment between the amputee""s residuum and the prosthesis and which reduces the portent of tissue damage and/or discomfort as well as reducing incidences of instability and insecurity due to poor fit.
It is even another object of this invention to provide a system that improves for the prosthetist the reliability of fitting suction-type sockets and reduces the extent of trial-and-error fitting.
It is still another object of this invention to provide a continuously adjustable prosthesis attachment to the anatomy, which accommodates natural, physiological volume changes of the amputee""s residuum.
It is yet another object of this invention to provide a means for employing and automatically regulating fluid fill in bladders within a prosthesis socket.
It is a further object of this invention to resolve stump-volume sensitivity.
It is still a further object of this invention to provide a means for increasing appliance volume for easy donning and doffing of the appliance.
It is another object of this invention to provide a dynamic variable geometry fitting system for maintaining secure fit of external appliances, such as shoes, boots, braces, wraps, garments to various body segments of humans and other animals.
It is a further object of this invention to provide a device for improving comfort of an external appliance applied to the body of humans and other animals by allowing dynamically adjustable pressure regulation.
The objects set forth above as well as further and other objects and advantages of the present invention are achieved by the embodiments of the invention described hereinbelow.
Briefly stated, the present invention provides a means for achieving dynamically variable geometry adjustable fit of an external appliance to a body segment of a human or other animal. For example, one embodiment of the present invention gives prosthetists a dynamic fitting system the use of which will provide lower-limb amputees with prostheses that maintain automatically a secure and comfortable fit throughout normal residuum volume fluctuation. The system employs the advantages of using incompressible fluid fill in the bladders rather than compressible gas fill. One or more of the bladders serves as a pump, energized by walking, for example, which is regulated by a control system. Once donned, the entire system requires neither manual intervention nor an outside power source to function. This embodiment of the present invention adjusts the socket volume automatically in order to maintain a proper fit on a transfemoral (TF) or transtibial (TT) residuum or other body-fitting appliances. However, the dynamic variable geometry fitting system is adaptable to other body appliances such as ski boot, boots (including sports boots), shoes, sneakers, prosthetic appliance, orthopedic appliance, brace, or body part wrap, and virtually anything that is designed to be worn on a body part.
For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description and its scope will be pointed out in the appended claims.